This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for Power Supply Of Display Apparatus With Universal Serial Bus Device earlier filed in the Korean Industrial Property Office on Apr. 11, 1998 and there duly assigned Serial No. 12976/1998.
1. Field of the Invention The present invention relates to power supply apparatus, and more particularly to a power supply of display apparatus having universal serial bus hub device.
2. Description of the Related Art
Display apparatus using cathode ray tubes have been used in the personal computer monitors for their high resolution and contrast. Despite technological developments in the display apparatus, the power consumption of the CRT monitor is still considerable. To reduce the monitor power consumption, most computer monitors have power saving function or xe2x80x9cgreenxe2x80x9d function as recommended by the Video Electronics Standard Association (VESA). The power saving function of the monitor is performed if there is no input to operate a computer system for a predetermined period of time. Complying with the Display Power Management Signaling (DPMS) scheme established by VESA, the video adapter of the computer system provides the monitor with the horizontal and vertical synchronization signals varied with the power saving modes between full-on, standby, suspend, and power-off state. It automatically reduces the power consumption of the monitor such that an amount of power is decreased with the lapse of time set by the DPMS control program.
In the full-on mode, both horizontal and vertical synchronization signals are in active state and are supplied with the display apparatus that allows normal operation of the display apparatus with consuming almost the power rating. In the standby mode, only vertical synchronization signal is in active state that allows the blank monitor screen with consuming less power than in the full-on mode. Further, in the suspend mode, only horizontal synchronization signal is in active state that allows the blank monitor screen with consuming much less power than in the standby mode. The power-off mode is the least power consumption level, which interrupts power supplies directed to all components in the display apparatus except the subsystem which can restore the system to the fill-on state. In this state, both horizontal and vertical synchronization signals are in inactive state.
In addition to this problem, during the power-offmode of DPMS, the power supply circuitry of the switching mode power supply (SMPS) will be operated continuously, which results in unnecessary power consumption in the display apparatus.
U.S. Pat. No. 5,799,196 for a Method and Apparatus of Providing Power Management Using a Self-Powered Universal Serial Bus (USB) Device to Flannery discloses how a computer system receives stand-by power from a peripheral bus incorporating a power source independent of the main power supply unit of the computer system. However, the disclosure does not use two power supplies. In addition, there appears to be no mechanism for shutting down power to the switching mode power supply or the main power supply when power to a peripheral is cut off.
U.S. Pat. No. 5,870,086 for a Power Saving Display Device and Method For Controlling Power Therefor to Bang discloses a main power circuit, an auxiliary power circuit, and a discriminator for discriminating whether the horizontal and vertical synchronous signals are inputted. However, there is no mention of power being supplied to a universal serial bus or any kind of bus during a power-down state.
U.S. Pat. No. 5,657,257 for a Power-Supply Controller of Computer to Lee discloses a power supply and a power controller to manage power to a computer. However, there is no mention of power being supplied to a universal serial bus or any kind of bus during a power-down state.
I have not seen a power supply that both supplies power to a universal serial bus hub and cuts off power to the switching mode power supply circuitry when the display device is in a power off state.
The present invention is intended to solve the prior art problems, and it is therefore an object of the invention to provide a power supply of display apparatus which can provide a stable supply power with the universal serial bus hub even if the display apparatus enters the power-off mode of DPMS.
It is another object of the invention to provide a power supply of display apparatus which can cut off power supply directed to the switching mode power supply circuitry when the display apparatus enters the power-off mode of DPMS.
In accordance with the present invention, the power supply comprises: a rectifier converting an AC input voltage into a DC output voltage; a first power supply circuitry for generating regulated output voltage required in the display apparatus when it receives the rectifier output voltage; a second power supply circuitry for supplying power with the USB hub, in which the second power supply circuitry is applied with the rectifier output voltage; a switch provided across the power line between the output of the rectifier and the input stage of the first power supply circuitry; and a controller in response to input status of the display power management signal corresponding to the power-off mode to produce a control signal that turns off the power line switch.
Further, the second power supply circuitry includes a DC/DC converter for outputting desired voltage to the USB hub.
Preferably, the display power management signal includes the horizontal and vertical synchronization signals (Hsync, Vsync) provided by the system host. Also, the power line switch includes a relay switch and relay drive circuitry, and wherein the relay switch uses an single pull single throw (SPST) normal-close switch.